Since a sensitive material has, in general, an outermost layer containing a hydrophilic colloid like gelatin as a binder, adhesion phenomenon under conditions of high temperature and high humidity readily occurs.
The term "adhesion phenomenon" as used herein describes the occurrence when sensitive materials superposed upon one another, or sensitive materials and substances brought into contact therewith, come to adhere to one another during the production, the photographic processing or the storage of the sensitive materials. This phenomenon frequently causes various disadvantages.
In order to solve this problem, various studies have been made. A well known approach for preventing the adhesion phenomenon consists in matting the surface layer by incorporating therein finely pulverized inorganic substances such as silicon dioxide, magnesium oxide, titanium dioxide, calcium carbonate, carbon black, etc., or fine particles of organic substances such as alkyl acrylates or methacrylates (e.g., polymethyl methacrylate, etc.), polystyrene, starch, etc., as disclosed in Japanese Patent Application (OPI) Nos. 23036/86 and 17743/87 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"). These fine particles are generally referred to as matting agents.
On the other hand, recent years have witnessed the acceleration of development processing of sensitive materials. The increased speed of development processing has necessarily caused an increase in the quantity of the processing solution brought by a sensitive material from the bath used in the preceding step into a processing bath subsequent thereto, and in its turn, has caused an accelerated deterioration of the processing bath. Moreover, the increased quantity of water carried out of the final processing bath has resulted in an increase in the drying load; so it has sometimes happened that the speed of photographic processing has been decreased.
Accordingly, various measures have been taken for the purpose of reducing the quantity of the processing solution carried out of a bath used in the preceding step into a bath to be used in the following step: For instance, one method adopted consists in the arrangement of a rubber board for the removal of water (so-called "rubber lips") or "a pair of opposing squeeze rollers" between adjacent processing baths and behind the final bath; thus, when a sensitive material is drawn through such devices, the processing solution which adhered to the sensitive material in the preceding step is scraped off.
As the speed of photographic processing of sensitive materials is increased, the degree of friction between the surface of the sensitive material and the rubber lip surface or the squeeze roller surface also increases. When known matting agents as described above are used, the strong rubbing of the sensitive material surface causes a problem in that the matting agent present in the outermost layer falls off.
As the matting agent continues to fall off, the degree of matting of the sensitive material which has completed the entire course of photographic processing decreases, whereby the sensitive material comes to be subject to adhesion to a different kind of substance or another sensitive material to result in various problems. For example, upon the contact exposure of an unexposed sensitive material through the processed sensitive material, "Newton ring" tends to generate because of the insufficiency in degree of matting. In addition, matting agents that have fallen off accumulate in development processing solutions to contaminate the processing solutions. Therefore, the life of the processing solutions are considerably shortened.
Moreover, it frequently happens that the matting agents which have fallen off accumulate on the rubber lip surface or the squeeze roller surface and condense there to grow into large agglomerated particles. Then, these agglomerated particles are transferred onto the surface of a sensitive material to be subsequently processed. The particles stuck to the surface fatally damage the image quality of the processed sensitive material.
Also, the agglomerated particles of matting agents accumulated on the rubber lip surface or the squeeze roller surface scratch the surface of sensitive materials traveling at a high speed during processing to result in generation of so-called "streaks". Once such streaks are generated, because of the rapidity of the traveling speed of sensitive materials in the photographic processing, a great number of defective sensitive materials are produced in a relatively short time, and thereby a heavy loss is caused.
For the above-described reasons, matting agents of the kind which hardly fall off by severe rubbing of the surface of a sensitive material during rapid development processing have been earnestly sought after.